Logic behind Old Buyer and New Buyer parameters of Reassign Purchasing Documents program

Summary: Wanted to understand the Logic behind Old Buyer and New Buyer parameters of Reassign Purchasing Documents program. What values this field holds and how those values are getting fetched.

Content (please ensure you mask any confidential information): Client wants to understand the Logic behind Old Buyer and New Buyer parameters of Reassign Purchasing Documents program. If Old buyer parameter LOV holds all the buyers including expired also and New Buyer parameter LOV holds only active buyers.

Version (include the version you are using, if applicable): 24A

Code Snippet (add any code snippets that support your topic, if applicable):